1. Field of the Invention
The present invention relates to an alternator driven by an internal combustion engine, and in particular, relates to a stator for an automotive alternator mounted to a vehicle such as a passenger car or a truck.
2. Description of the Related Art
Conventionally, a stator winding in a stator for an automotive alternator is manufactured by preparing an annular coil by winding continuous wire into an annular shape, preparing a star shape coil by deforming this annular coil into a star shape, and then installing straight portions of this star shape coil into slots in a stator core. However, excessive stress is applied to the wire when installing the star shape coil in the slots of the stator core, increasing the likelihood of wire breakage or insulation defects, and productivity has been markedly inferior.
Thus, in order to solve such deficiencies, a method for manufacturing stator windings by first bending an electric conductor into U-shaped segments and inserting a number of these segments into the slots in the stator core, and then joining end portions of these segments extending outwards from the slots, has been proposed in Japanese Patent Laid-Open No. HEI 11-164506, for example.
FIG. 13 is a plan showing connection of one phase of a stator winding in the stator for an automotive alternator disclosed in Japanese Patent Laid-Open No. HEI 11-164506, for example, FIG. 14 is a schematic perspective of segments constituting the stator winding, and FIGS. 15 to 17 are developed projections each showing a portion of the connections of one phase of the stator winding.
The stator 8 in FIG. 13 includes: a stator core 15; and a stator winding 16 composed of a number of segments 30 arranged in slots 15a formed in the stator core 15. In this case, thirty-six slots 15a are formed in the stator core 15 at even pitch so as to house three phases of windings therein corresponding with the number (12) of magnetic poles in a rotor (not shown).
The segments 30 are inserted two at a time from a first axial end of the stator core 15 into pairs of slots 15a which are three slots apart (a pitch of one magnetic pole). Then, the stator winding 16 is constructed by joining end portions of the segments 30 extending outwards from a second axial end of the stator 15 in a predetermined pattern. Moreover, the segments 30 are accommodated so as to line up in a row of four in a radial direction within each slot 15a. Hereinafter, the four segment accommodating positions lined up in the radial direction within each slot 15a will be numbered from an outer circumferential side as first, second, third, and fourth positions, respectively.
As shown in FIG. 14, large segments 31 and small segments 32, each composed of an electric conductor such as insulated copper having a rectangular cross section formed into a general U shape, are used for the segments 30.
The small segments 32 are inserted from the first axial end into the second positions within first slots 15a and into the third positions within second slots 15a three slots away from the first slots 15a in a clockwise direction in FIG. 13. The large segments 31 are similarly inserted from the first axial end into the first positions within the first slots 15a and into the fourth positions within the second slots 15a three slots away from the first slots 15a in the clockwise direction in FIG. 13. Thus, straight portions 31a and 32a of the large and small segments 31 and 32 are arranged so as to line up in a row in a radial direction within each of the slots 15a.
At the first axial end of the stator core 15, turn portions 31c of the large segments 31 surround outer circumferential sides of turn portions 32c of the small segments 32 inserted into the same pairs of slots 15a. The turn portions 31c and 32c are arranged to line up in rows in a circumferential direction and constitute a second coil-end portion 16b.
At the second axial end of the stator core 15, end portions 32b of the small segments 32 extending outwards from the second axial end from the second positions within the first slots 15a are joined to end portions 31b of the large segments 31 extending outwards from the second axial end from the first positions within the second slots 15a three slots away from the first slots 15a in the clockwise direction in FIG. 13, and end portions 31b of the large segments 31 extending outwards from the second axial end from the fourth positions within the first slots 15a are joined to end portions 32b of the small segments 32 extending outwards from the second axial end from the third positions within the second slots 15a three slots away from the first slots 15a in the clockwise direction in FIG. 13. The joint portions formed by joining the end portions 32b of the small segments 32 extending outwards from the second axial end from the second positions within the slots 15a to the end portions 31b of the large segments 31 extending outwards from the second axial end from the first positions within the slots 15a and the joint portions formed by joining the end portions 31b of the large segments 31 extending outwards from the second axial end from the fourth positions within the slots 15a to the end portions 32b of the small segments 32 extending outwards from the second axial end from the third positions within the slots 15a line up radially, are arranged to line up in rows in a circumferential direction and constitute a first coil-end portion 16a.
The method of winding one phase (the X phase) of the stator winding 16 will now be explained with reference to FIGS. 15 to 17. Moreover, in each of the figures, electric conductors disposed on the outermost circumference in a radial direction are represented by doubledotted chain lines, electric conductors disposed in the second position from the outer circumference in the radial direction are represented by solid lines, electric conductors disposed in the third position from the outer circumference in the radial direction are represented by broken lines, and electric conductors disposed in the fourth position from the outer circumference in the radial direction are represented by, a single-dotted chain lines. Furthermore, the upper level represents the second coil-end portion 16b composed of arranged turn portions, and the lower level represents the first coil-end portion 16a composed of arranged joint portions. The horizontal row of numbers in the center of each diagram are slot numbers.
First, as shown in FIG. 15, large and small segments 31 and 32 are inserted into every third slot from slot number 1. In the first coil-end portion 16a, the end portions 32b of the small segments 32 extending outwards from the second positions within the first slots 15a are joined to the end portions 31b of the large segments 31 extending outwards from the first positions of the second slots 15a three slots away in the clockwise direction in FIG. 13, and end portions 31b of the large segments 31 extending outwards from the fourth positions of the first slots 15a are joined to end portions 32b of the small segments 32 extending outwards from the third positions of the second slots 15a three slots away in the clockwise direction in FIG. 13. Then, the turn portions 31c and 32c of the large and small segments 31 and 32 inserted into slot numbers 1 and 34 are cut.
In this manner, a lap-wound first winding sub-portion 161 is formed having two turns per slot. At the same time, a lap-wound second winding sub-portion 162 is formed having two turns per slot as shown in FIG. 16. As shown in FIG. 17, the first and second winding sub-portions 161 and 162 are joined (by a bridging connection) between a second end portion 161b of the first winding sub-portion 161 and a first end portion 162a of the second winding sub-portion 162 to form one phase of the stator winding 16, the phase having four turns. A first end portion 161a of the first winding sub-portion 161 and a second end portion 162b of the second winding subportion 162 become a lead wire (O) and a neutral point (N) respectively.
Moreover, the cut ends of the large segment 31 correspond to the end portions 162a and 162b of the second winding sub-portion 162, and the cut ends of the small segment 32 correspond to the end portions 161a and 161b of the first winding sub-portion 161. Furthermore, the joint portion formed by joining the second end portion 161b of the first winding sub-portion 161 to the first end portion 162a of the second winding sub-portion 162 becomes a bridging connection connecting portion (C).
In addition, two other phases (Y and Z) of the stator winding 16 are offset by one slot and manufactured similarly.
Then, the three phases of the stator winding 16 are formed into an alternating current connection by connecting the neutral points (N) of each phase of the stator winding 16 to each other and connecting the lead wires (O) to a rectifier (not shown).
Now, because the end portions 161a and 161b of the first winding sub-portion 161 and the end portions 162a and 162b of the second winding sub-portion 162 are obtained by cutting the turn portions 31c and 32c of large segments 31 and small segments 32, the segments constituting the end portions 161a and 161b of the first winding sub-portion 161 and the end portions 162a and 162b of the second winding sub-portion 162 are different from the other large segments 31 and small segments 32. In other words, each phase of the stator winding 16 has four differently-shaped segments disposed two at a time into pairs of slots separated by the pitch of one magnetic pole. After the turn portions 31c and 32c of some of the large segments 31 and some of the small segments 32 are cut, these differently-shaped segments are formed into bridging connections or three-phase alternating current connections.
As explained above, in this conventional stator 8 for an automotive alternator, each phase of the stator winding 16 has four differently-shaped segments disposed two at a time into pairs of slots separated by the pitch of one magnetic pole. When these differently-shaped segments are formed into bridging connections or three-phase alternating current connections or connected to the rectifier after the turn portions 31c and 32c of some of the large segments 31 and some of the small segments 32 are cut, twisting, pulling, etc., are applied to the differently-shaped segments, leading to a risk of the insulation on the electric conductors in the slots 15a or the insulation on the electric conductors constituting the coil ends being damaged, and one problem has been that short circuiting arises easily, reducing quality.
Furthermore, another problem has been that because the first winding sub-portion 161 and the second winding sub-portion 162 are not formed in the same shape, the same processing jig cannot be used for both the lead wire (O) and the neutral point (N), reducing productivity.